Neville Longbottom faints at the sound of screeching mandrake roots and can’t even win against feisty Cornish pixies, which grab him by the ears and hang him by a classroom ceiling fan. But the “Harry Potter” series’ crooked-toothed class clown at Hogwarts School of Witchcraft and Wizardry proves a true leader in the fight against evil, and he even gets a Yule Ball date before Harry does.

Margaret Smith

Neville Longbottom faints at the sound of screeching mandrake roots and can’t even win against feisty Cornish pixies, which grab him by the ears and hang him by a classroom ceiling fan.

But the “Harry Potter” series’ crooked-toothed class clown at Hogwarts School of Witchcraft and Wizardry proves a true leader in the fight against evil, and he even gets a Yule Ball date before Harry does.

British-born actor Matthew Lewis, 20, has played Neville throughout the film series.

Lewis, who appeared in Boston to promote the opening of “Harry Potter: The Exhibition” at the Museum of Science, spoke briefly about playing one of the series’ most unlikely heroic figures.

Q. In most of the films so far, Neville Longbottom is a supporting character with limited appearances. How do you establish the character so he is memorable?

A. I’m always in contact with [director] David Yates, and we talk constantly about what Neville would be doing and feeling, even when he is in the background. … This is something David Yates is keen about, not just with Neville Longbottom, but with all the characters, to keep the whole scene alive.

Q. As someone who was a fan of the books since childhood, is there anything in the movies so far that you wish were different?

A. I was a little upset when the scene in the book “Harry Potter And The Order of The Phoenix” wasn’t included where Neville goes to St. Mungo’s Hospital to see his parents [torture victims of Bellatrix Lestrange, follower of Lord Voldemort]. That scene was so crucial to Neville’s character. But due to the length of the film, we had to cut that sequence.

Q. The stories – the books and the films – are told mainly from Harry’s point of view. Does this limit the ability to tell the story?

A. Obviously, the books are about Harry Potter – how he was orphaned, how he grew up, how he thought at first that he was a Muggle [a person who cannot do magic.] … His interactions with the other characters really touched me a lot – with Neville, he helps bring him out of his shell. His interactions with Neville have helped bring Neville along.

Q. Along with the main characters, it seems like nearly every supporting character, including Neville, has a fan base. Does that have an effect on how you play the character?

A. [Laughs.] People do say, “More Neville, please. It’s a shame there isn’t more of him in the film.” In the last film [“Harry Potter And The Half-Blood Prince,”] Neville only had two lines. I would have liked more, but it is such a massive story that some characters had to take more of a backseat role. Also, there were new characters that had to be introduced.

Q. There are people who write fan fiction about characters, including Neville, with alternate endings and realities. Are you familiar with any of these stories?

A. I have been given some fan fiction by various fans. It is interesting. Some of it is downright strange. But if people like the character so much and write their own back stories, I think it is wonderful. If the fans feel they know the character enough to write a complete different story, then that is wonderful.

Q. Some fans also have a crush on Neville and on you. Did you ever expect that?

A. Definitely not for myself, but I wouldn’t begrudge it. [Laughs.] It’s cool for a 20-year-old guy to have that. When I got into “Harry Potter,” that was never really the aim.

Q. What can we expect from Neville in the next film [“Harry Potter And The Deathly Hallows, Part One, to be released in 2010]?

A. I got the final script a few weeks ago. Neville has got a lot of stuff to do. The three main students [Harry, and friends Ron Weasley and Hermoine Grainger] have been away from Hogwarts, but Neville stays and takes charge of Dumbledore’s Army [which leads the charge against Voldemort and his forces.] He is leading an underground resistance. He gets beaten and is a bit bloodied.